Pre-virtualization: Soft layering for virtual machines

Abstract

Para-virtualization ties a guest operating system and a hypervisor together, which restricts the system architecture; e.g., when Linux uses the Xen API, Linux is unable to run on alternative hypervisors such as VMware, Linux itself, or a security kernel such as EROS. Furthermore, the lock-in obstructs evolution of its own paravirtualization interface -virtual machines provide the vital ability to run obsoleted operating systems alongside new operating systems, but para-virtualization often lacks this feature, requiring all concurrent instances to be the hypervisor's supported version. Even general purpose operating systems have weaker restrictions for their applications. This lock-in discards the modularity of virtualization; modularity is an intrinsic feature of traditional virtualization, helping to add layered enhancements to operating systems, especially when enhanced by people outside the operating system's development community (e.g., Linux server consolidation provided by VMware).Virtualization and its modularity solve many systems problems; combined with the performance of paravirtualization it becomes even more compelling. We show how to achieve both together. We offer a set of design principles, which we call soft layering, that govern the modifications made to the operating system. Additionally, our approach is highly automated, thus reducing the implementation and maintenance burden of paravirtualization, which is especially useful for enabling obsoleted operating systems. We demonstrate soft layering on x86 and Itanium: we can load a single Linux binary on a variety of hypervisors (and thus substitute virtual machine environments and their enhancements), while achieving essentially the same performance as para-virtualization with less effort.

Energy-Efficient Mapping Technique for Virtual Cores

“…The L4 µ-kernel [39] is a pre-virtualization system [40] which slightly modifies the guest operating systems such that the guest operating systems run upon the µ-kernel as userlevel applications and have the performance which is comparable to that of the native operating systems [22]. Therefore, in addition to personal computers and/or enterprise systems, the L4 µ-kernel is also applicable to embedded systems.…”

Proteus Hypervisor: Full Virtualization and Paravirtualization for Multi-core Embedded Systems

“…By mapping a specific set of privileged registers into VM's memory space, no trap to the hypervisor is required to access these registers. Previrtualization (Pre V) is an approach to paravirtualize guests automatically [16]. The source code is analyzed at compile time in order to identify privileged instructions.…”

SymCall

“…There are currently two approaches taken by existing virtualization tools: full system virtualization [19,25,26] and paravirtualization [1,3,17,27]. In fact it is quickly becoming the case that these approaches are no longer mutually exclusive.…”